European stocks had their worst day in months as unrest threatened to boil over in Greece, where deep budget cuts have eroded people's living standards, and Spain, where citizens are resisting a likely bailout from international lenders. Earlier, Asian stocks closed lower.

The euro fell sharply against the dollar, and the price of oil closed below $90 per barrel for the first time since early August.

Rising demand for lower-risk investments fed strong bids for U.S. Treasury debt. The yield on the 10-year Treasury note fell to 1.62 percent from 1.67 percent late Tuesday. A bond's yield falls as its price increases.

The Dow Jones industrial average fell 44.04 points, or 0.3 percent, to 13,413.51. The S&P 500 index fell 8.27, or 0.6 percent, to 1,433.32. The only category that rose was utilities, relatively safe stocks that tend to hold their value when the economy is weak.